1. Field of the Invention
The present invention relates to the arrangement of a breather chamber of an overhead valve type internal combustion engine, for locating a cam shaft, rotatably driven by a transmission member such as a chain, in a cylinder head.
2. Description of Background Art
Japanese Patent laid-open No. Sho 58-93914 discloses technology related to the arrangement of a breather chamber of an overhead valve type internal combustion engine. In this related art technology, in an overhead valve V-type two cylinder internal combustion engine having a cam shaft rotatably supported in a cylinder head, a breather chamber is arranged in a space caused by an offset between the two cylinders arranged in a V shape, and is formed between a cylinder bore formed in a cylinder and a chain chamber housing a chain for driving a cam. Also, the breather chamber and the chain chamber are formed spread across a crankcase, a cylinder and a cylinder head.
In the above described related art technology, the breather chamber is arranged taking advantage of a space already formed by the cylinder arrangement peculiar to V-type internal combustion engines, which means that there is no need to make a new space in order to arrange the breather chamber. However, with respect to the chain chamber, the cylinder bore and the breather changer are arranged in series, which means that if this arrangement is adopted by a third party in an internal combustion engine having a cylinder arrangement that is other than V-type or horizontally opposed, there will be a need to make a new space in order to arrange the breather chamber between the chain chamber and the cylinder bore, and the internal combustion engine will become large.
The present invention therefore aims to provide an overhead valve type internal combustion engine that is V-type or horizontally opposed, or indeed an overhead valve type internal combustion engine having any other cylinder arrangement, in which a breather chamber having a required capacity can be arranged without increasing the size of the engine, by taking advantage of a space that has already been formed.
A first aspect of the present invention is an overhead valve type internal combustion engine, comprising a cylinder bore formed in a cylinder, a freely rotatable cam shaft located in a cylinder head, and also located to the side of the cylinder bore viewed from a direction of a centerline of the cylinder, a housing chamber, located to the side of the cylinder bore, for housing a transmission member for rotationally driving the cam shaft, and a breather chamber located so as to be below the cam shaft and parallel to the cylinder bore on one side of the housing chamber.
According to this first aspect of the present invention, since a freely rotatable cam shaft located in the cylinder head is located to the side of the cylinder bore viewed from the direction of a centerline of the cylinder, a space is formed at the side of the cylinder below the cam shaft. Also, the breather chamber is located so that it is parallel to the cylinder bore at the same side of the housing chamber for housing the transmission member for rotationally driving the cam shaft where the cylinder bore is located. As a result, the breather chamber is arranged taking advantage of a space that already exists formed below the cam shaft which means that there is no need to make a new space in order to arrange the breather chamber. This means that it is possible to arrange a breather chamber having the required capacity without increasing the size of the engine.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.